Superlega IN792 DS: Ottimizzazione della saldatura EB e laser e dei trattamenti post saldatura

Nickel-based superalloys are widely used in the fabrication of high temperature components (discs and vanes) of aeronautical turbines and power plants. Their structure consists, quite simply, of two phases: a disordered matrix (phase ã) reinforced by a second ordered intermetallic phase precipitation, i.e: Ni3 (Al, Ti) phase ã'. In service operation, the nickel superalloy mechanical parts are subject to surface cracking. Given the high cost production, their repair by welding/remelting with material adduction can be a valid solution for the life extension of the components. This paper presents the results of electron beam and laser beam repair welding optimization through re-melting tests analysis conducted on 2 mm thick plates obtained from a directionally solidified IN792 ingot (DS). The results show how, both with EBW and LBW, a preheating (PHT) at 300 °C is necessary to avoid hot cracking initiation followed by a subsequent post-weld heat treatment (PWHT) for stress relieving. For both techniques, the microstructure shows how the ratio between ã'/ã phases goes from 70/30 of the base material to 30/70 of the fused zone (ZF). It has been possible to realize crack-free remelting, however the laser technique (LBW) remains more susceptible to the porosity compared to the electron beam welding (EBW). © 2018 Instituto Italiano della Saldatura. All rights reserved.